Fluorescence and lasing of neutral nitrogen molecules inside femtosecond laser filaments in air: mechanism and applications.

High power femtosecond laser pulses launched in air undergo nonlinear filamentary propagation, featuring a bright and thin plasma channel in air with its length much longer than the Rayleigh length of the laser beam. During this nonlinear propagation process, the laser pulses experience rich and complex spatial and temporal transformations. With its applications ranging from supercontinuum generation, laser pulse compression, remote sensing to triggering of lightning, the underlying physical mechanism of filamentation has been intensively studied. In this review, we will focus on the fluorescence and cavity-free lasing effect of the plasma filaments in air. The different mechanisms underlying the fluorescence of the excited neutral nitrogen molecules will be throughly examined and it is concluded that the electron collision excitation is the dominant channel for the formation of the excited nitrogen molecules. The recently discovered "air lasing" effect, a cavity-free bidirectional lasing emission emitted by the filaments, will be introduced and its main properties will be emphasized. The applications of the fluorescence and lasing effect of the neutral nitrogen molecules will be introduced, with two examples on spectroscopy and detection of electric field. Finally, we discuss the quenching effect of the lasing effect in atmosphere and the mechanisms responsible will be analyzed. An outlook for the achievement of backward lasing in air will be briefly presented.

Conservation of orbital angular momentum throughout amplification of high order harmonics in Ni-like krypton and silver plasmas.

In this article we present modelling results of the amplification of High Order Harmonics (HOH) carrying orbital angular momentum (OAM) in plasma amplifiers created from krypton gas and silver solid targets. The resulting amplified beam is characterized in terms of intensity, phase and decomposition in helical and Laguerre-Gauss modes. Results show that the amplification process conserves OAM, although some degradation is apparent. Several structures appear in the intensity and phase profiles. These structures have been characterized with our model and related to refraction and interference with the plasma self-emission. Thus, these results not only demonstrate the capability of plasma amplifiers to deliver HOH amplified beams carrying OAM but also pave the way towards using HOH carrying OAM as a probe beam to diagnose the dynamics of hot, dense plasmas.

3D modelling of cavity-free lasing in nitrogen plasma filaments.

In this article we show results on cavity-free lasing in nitrogen filaments using our 3D, time-dependent Maxwell-Bloch code, Dagon. This code was previously used to model plasma-based soft X-ray lasers and it has been adapted to model lasing in nitrogen plasma filaments. In order to assess the predictive capabilities of the code, we have conducted several benchmarks against experimental and 1D modelling results. Afterwards, we study the amplification of an externally seeded UV beam in nitrogen plasma filaments. Our results show that the phase of the amplified beam carries information about the temporal dynamics of amplification and collisional processes inside the plasma, along with information about the spatial structure of the amplified beam and the active region of the filament. We thus conclude that measuring the phase of an UV probe beam, in combination with 3D Maxwell-Bloch modelling, might be an excellent method for diagnosing electron density value and gradients, mean ionization, density of N2+ ions and the magnitude of collisional processes inside these filaments.

Spectral splitting of the lasing emission of nitrogen ions pumped by 800-nm femtosecond laser pulses.

We report on a spectral splitting effect of the cavity-less lasing emission of nitrogen ions at 391.4 nm pumped by 800-nm femtosecond laser pulses. It was found that with the increase of the nitrogen gas pressure and pump pulse energy, both R and P branches experience spectral splitting. With an external injected seeding pulse, a similar split spectral line is observed for the amplified emission. In contrast, for the fluorescence radiation, no such spectral splitting phenomenon is observed with much more abundant R branch structures. Our theoretical model considers gas ionization by the pump pulse, the competition of excitation of all relevant electronic and vibrational states, and an amplification of the seeding pulse in the plasma with a population inversion. Our simulation reproduces this spectral splitting effect, which is attributed to the gain saturation resulting in the oscillation of the amplitude of the amplified signal.

Formation Dynamics of Excited Neutral Nitrogen Molecules inside Femtosecond Laser Filaments.

Nitrogen molecules are promoted to excited neutral states during femtosecond laser pulse filamentary propagation in atmosphere, leading to a characteristic UV fluorescence. Using a laser-induced fluorescence depletion technique, we measure the formation dynamics of these excited neutral nitrogen molecules with femtosecond time resolution. We find that the excited neutral molecules are formed in an unexpected ultrafast timescale of ∼4 ps at 1 bar and ∼120 ps at 30 mbar pressure. From this observation we deduce that the excitation of neutral N_{2} occurs via multiple collisions with hot free electrons. Numerical simulations based on rate equations reproduce well this ultrafast formation time and its dependence on gas pressure, and thus support this interpretation.

Hydrodynamic evolution of plasma waveguides for soft-x-ray amplifiers.

High-density, collisionally pumped plasma-based soft-x-ray lasers have recently delivered hundreds of femtosecond pulses, breaking the longstanding barrier of one picosecond. To pump these amplifiers an intense infrared pulse must propagate focused throughout all the length of the amplifier, which spans several Rayleigh lengths. However, strong nonlinear effects hinder the propagation of the laser beam. The use of a plasma waveguide allows us to overcome these drawbacks provided the hydrodynamic processes that dominate the creation and posterior evolution of the waveguide are controlled and optimized. In this paper we present experimental measurements of the radial density profile and transmittance of such waveguide, and we compare them with numerical calculations using hydrodynamic and particle-in-cell codes. Controlling the properties (electron density value and radial gradient) of the waveguide with the help of numerical codes promises the delivery of ultrashort (tens of femtoseconds), coherent soft-x-ray pulses.

Backward Lasing of Air plasma pumped by Circularly polarized femtosecond pulses for the saKe of remote sensing (BLACK).

Recently, S. Mitryukovskiy et al. presented experimental evidence showing that backward Amplified Spontaneous Emission (ASE) at 337 nm can be obtained from plasma filaments in nitrogen gas pumped by circularly polarized 800 nm femtosecond pulses (Opt. Express, 22, 12750 (2014)). Here, we report that a seed pulse injected in the backward direction can be amplified by ~200 times inside this plasma amplifier. The amplified 337 nm radiation can be either linearly or circularly polarized, dictated by the seeding pulse, which is distinct from the non-polarized nature of the ASE. We performed comprehensive measurements of the spatial profile, optical gain dynamics, and seed pulse energy dependence of this amplification process. These measurements allow us to deduce the pulse duration of the ASE and the amplified 337 nm radiation as well as the corresponding laser intensity inside the plasma amplifier. It indicates that the amplification is largely in the unsaturated regime and that further improvement of laser energy is possible. Moreover, we observed optical gain in plasma created in ambient air. This represents an important step towards future applications exploiting backward lasing for remote atmospheric sensing.

Wavefront improvement in an injection-seeded soft x-ray laser based on a solid-target plasma amplifier.

The wavefront of an injection-seeded soft x-ray laser beam generated by amplification of high-harmonic pulses in a λ=18.9 nm molybdenum plasma amplifier was measured by a Hartmann wavefront sensor with an accuracy of λ/32 root mean square (rms). A significant improvement in wavefront aberrations of 0.51±0.03λ rms to 0.23±0.01λ rms was observed as a function of plasma column length. The variation of wavefront characteristic as a function time delay between the injection of the seed and peak of soft x-ray amplifier pump was studied. The measurements were used to reconstruct the soft x-ray source and confirm its high peak brightness.

Soft x-ray plasma-based seeded multistage amplification chain.

To date, plasma-based soft x-ray lasers have demonstrated experimentally 1 µJ, 1 ps (1 MW) pulses. This Letter reports extensive study using time-dependant Maxwell-Bloch code of seeding millimeter scale plasmas that store more than 100 mJ in population inversion. Direct seeding of these plasmas has to overcome very strong amplified spontaneous emission (ASE) as well as prevent wake-field amplification. Below 100 nJ injected energy, seed produces pulses with picosecond duration. To overcome this limitation, a new scheme has been studied, taking advantage of a plasma preamplifier that dramatically increases the seed energy prior to entering the main plasma amplifier leading to ASE and wake-free, fully coherent 21.6 µJ, 80 fs pulses (0.27 GW).

Impacto de la trombólisis en pacientes con infarto agudo del miocardio en la atención primaria de salud / Thrombolysis impact on patients with acute myocardial infarction in primary health care

Se realizó un estudio de evaluación en el municipio de Julio Antonio Mella, perteneciente a la provincia de Santiago de Cuba, con vistas a determinar el impacto de la trombólisis a partir del grado de aceptabilidad del tratamiento, así como la satisfacción de la población por recibirlo y de los prestadores de salud por brindarlo. La investigación abarcó desde enero de 2009 hasta igual mes de 2010 e incluyó a 26 pacientes mayores de 15 años, los cuales acudieron a la institución sanitaria con un cuadro de infarto agudo del miocardio y criterio establecido de aplicar esa modalidad terapéutica. Se crearon los indicadores y estándares pertinentes, así como se aplicaron las pruebas de Fisher y V de Cramer para la validación estadística. Entre los principales resultados sobresalieron que la trombólisis en la atención primaria de salud fue muy bien acogida por los pobladores del área, pero no por un reducido número de quienes la efectuaron, aunque ello no impidió que en sentido general fuese muy elevado el nivel de satisfacción de ambas partes por el promedio de tratamientos útiles logrados, si bien convendría disminuir el tiempo de asistencia prehospitalaria para obtener una mayor efectividad de la medicación trombolítica.

An assessment study was carried out in Julio Antonio Mella municipality from Santiago de Cuba province in order to determine thrombolysis impact starting from the therapy acceptability degree, as well as from the population satisfaction for receiving it and from health workers for providing it. Investigation was carried out from January, 2009 to January, 2010 and it included 26 patients over 15 years, who went to the health institution undergoing acute myocardial infarction and followed the established criterion of applying this therapeutic modality. Appropriate indicators and standards were created. Furthermore, Fisher's Exact and V Cramer's tests were applied for the statistics validation. Thrombolysis in primary health care resulted relevant among the main results because this procedure was well accepted by inhabitants of the area, but not by some of those who performed it. Anyway, this situation did not hinder that satisfaction level for both parts resulted high in general sense due to the average of useful therapies achieved, although reducing the previous hospital care in order to obtain a higher effectiveness of thrombolytic medication would be advisable.

Hydrodynamic study of plasma amplifiers for soft-x-ray lasers: a transition in hydrodynamic behavior for plasma columns with widths ranging from 20 µm to 2 mm.

Plasma-based seeded soft-x-ray lasers have the potential to generate high energy and highly coherent short pulse beams. Due to their high density, plasmas created by the interaction of an intense laser with a solid target should store the highest amount of energy density among all plasma amplifiers. Our previous numerical work with a two-dimensional (2D) adaptive mesh refinement hydrodynamic code demonstrated that careful tailoring of plasma shapes leads to a dramatic enhancement of both soft-x-ray laser output energy and pumping efficiency. Benchmarking of our 2D hydrodynamic code in previous experiments demonstrated a high level of confidence, allowing us to perform a full study with the aim of the way for 10-100 µJ seeded soft-x-ray lasers. In this paper, we describe in detail the mechanisms that drive the hydrodynamics of plasma columns. We observed transitions between narrow plasmas, where very strong bidimensional flow prevents them from storing energy, to large plasmas that store a high amount of energy. Millimeter-sized plasmas are outstanding amplifiers, but they have the limitation of transverse lasing. In this paper, we provide a preliminary solution to this problem.

Resistência à flexão de porcelanas feldspáticas convencionais processadas por injeção / Flexural strength of heat-pressing feldspathic porcelains

O objetivo deste estudo foi investigar o efeito do processamento por injeção (método da cera perdida) na resistência à flexão, em três pontos, de porcelanas feldspáticas convencionalmente obtidas por sinterização. Foram avaliadas as porcelanas Ceramco-2, Duceragold, Duceram-Plus, Excelsior, Omega-900, Symbio, Vitadur-Alpha e VMK-95. Como controle, foi também utilizada a porcelana Cergogold, fornecida na forma de pastilhas pré-sinterizadas e processada exclusivamente por injeção. Corpos de prova em forma de barra (n = 10), com dimensões de 25 × 5 × 2 mm (ISO-6872), foram confeccionados em matrizes metálicas e processados, por sinterização ou injeção, nas temperaturas de cocção indicadas pelos fabricantes. Os ensaios foram realizados em equipamento MTS-810 (Material Test System, EUA), com célula de carga de 10 kN e velocidade de 0,5 mm.min-1. Os resultados, submetidos à análise de variância (p menor ou igual a 0,05), mostraram que o processamento por injeção foi capaz de proporcionar maior resistência à fexão para as porcelanas Duceram-Plus, Excelsior, Omega-900, Symbio e VMK-95 (p < 0,001). Nessa mesma condição experimental, a porcelana Cergogold mostrou-se estatisticamente superior apenas à porcelana Vitadur-Alpha, sendo inferior à porcelana Omega-900 e semelhante às demais (p < 0,001). A resistência à fexão das porcelanas Ceramco-2, Duceragold e Vitadur-Alpha não foi influenciada pelo processo de obtenção (p < 0,001).

The aim of this study was to evaluate the effect of injection process, on the three-point flexural strength on feldspathic ceramic, fabricated by sintering technique. The ceramics evaluated were Duceragold, Duceram Plus, Excelsior, Omega 900, Symbio,Vitadur Alpha, VMK 95 and Ceramco 2. Cergogold, that the processing technique is based on a conventional injection moulding, was used for control. The bar-shaped specimens (n = 10) with the size of 25 × 5 × 2 mm (ISO-6872) were fabricated in a metal mould and processed by injection or sinterized, according to manufacturing specifcations. The fexural test was performed in a MTS 810 testing machine (Material Test System, USA), with a 10 kN load cell and a crosshead speed of 0.05 mm.min-1. The data (MPa) were subjected to analysis of variance (p less than or equal to 0.05), and showed that the injection processed enhance the flexural strength of Duceram-Plus, Excelsior, Omega-900, Symbio and VMK-95 (p < 0.001). In this experimental condition, the ceramic Cergogold showed high value than Vitadur-Alpha, was inferior to the ceramic Omega-900, but there were no signifcant difference with the others (p < 0.001). The flexural strength was not influenced by the processing method for the ceramics Ceramco-2, Duceragold and Vitadur-Alpha.

Pilar personalizado em zircônia: relato de caso clínico / Customized zirconia abutment: case report report

Pilares metálicos têm sido amplamente utilizados em reabilitações implanto-suportadas ao longo dos anos. No entanto, estes componentes preenchem apenas parcialmente os requisitos estéticos e biológicos necessários para o sucesso das próteses sobre implantes. A utilização das cerâmicas odontológicas para pilares e coroas provê melhor translucidez e biocompatibilidade se comparada à combinação entre pilares metálicos e restaurações metalocerâmicas. Além disso, evitam o escurecimento geralmente associado com componentes metálicos, transmitidos através dos tecidos peri-implantares. A introdução de pilares cerâmicos à base de alumina possibilitou a confecção de restaurações totalmente livres de metal, com propriedades ópticas semelhantes ao dente natural e maior lisura de superfície, diminuindo a agregação bacteriana. Apesar das vantagens, estes pilares apresentavam problemas como radiolucidez em exames radiográficos, para análise da adaptação após assentamento e relativamente baixa resistência à fratura. Assim, hoje estão sendo introduzidos no mercado pilares com incorporação de óxido de zircônia, possibilitando a ampliação do uso de pilares estéticos pelo aumento da resistência à fratura a níveis comparados aos pilares metálicos. Desta forma, este artigo tem o objetivo de relatar uma reabilitação unitária implantossuportada utilizando um novo pilar cerâmico à base de zircônia.

Metal implant abutments have been widely used in implant-supported restorations for years. Though, such abutments only partially fulfill the esthetic and biological requirements needed for successful implant prostheses. The use of dental ceramics for abutments and crowns would provide better translucency and biocompatibility compared to combination of metal abutments and ceramometal crowns. They also eliminate the metal shining, generally associated with metal components, transmitted through peri-implant tissues. The introduction of alumina-based ceramic abutments provided all-ceramic implant restorations with optical properties similar to natural tooth and increased surface smoothness, minimizing bacterial aggregation. Although it had advantages, this abutment presented problems such as radiolucency at the time of radiologic examination of marginal adaptation and relatively low fracture resistance. Recently, zirconium oxide abutments have been introduced and increased ceramic abutment applications due to its high fracture resistance similar to metal abutments. The aim of the present study is to report a single unit implant-supported restoration utilizing a new zirconia-based ceramic abutment.

Strategies for competitiveness and sustainability: adaptation of a Brazilian subsidiary of a Swedish multinational corporation.

The competitiveness, in terms of macro and micro levels of an enterprise, is often dictated by its capacity to innovate, ability to respond to the needs of the market, and resilience to challenges from competition. This paper reviews the literature on the adaptation of research and development (R&D) units in subsidiaries of multinational corporations. It focuses mainly on the impact of the technological dynamic on sustainability performance of the Brazilian subsidiary of the Swedish multinational Ericsson. Through a conceptual framework, it explores information and communication technologies (ICT) towards a transversal and comprehensive vision of levels of innovation and sustainability.

Utilização de programas de computador 3-D como auxiliares no planejamento do tratamento do edentulismo maxilar / The use of 3-D software computer systems as an auxiliary method for treatment planning of the maxillary edentulism

O tratamento reabilitador da maxila edêntula tem sido discutido de maneira intensa nas publicações científicas atuais, assim como tem sido tema de inúmeras apresentações em congressos específicos na área de Implantodontia nas diversas partes do mundo. Diferentes filosofias e possibilidades terapêuticas têm sido apresentadas, com variados graus de complexidade, morbidade, custos e evidência científica. Os procedimentos reabilitadores da maxila edêntula podem ser divididos em dois grandes grupos: as técnicas de ancoragem, onde podemos destacar os implantes inclinados e as fixações zigomáticas; e as técnicas reconstrutivas que englobam as diversas modalidades de enxerto ósseo. Este artigo tem como finalidade discutir a utilização de programas tridimensionais digitais como auxiliares no planejamento do tratamento reabilitador da maxila edêntula, otimizando as possibilidades clínicas do uso da ancoragem alveolar num número maior de pacientes.

Tratamento do edentulismo total mandibular com a técnica de cirurgia guiada sem retalho / The edentudous lower jaw treatment using the flapless guided surgery

O planejamento reabilitador tridimensional da mandíbula edêntula utilizando softwares especialmente desenvolvidos para a Implantodontia, tem viabilizado a realização de técnicas cirúrgicas minimamente invasivas através da utilização de guias cirúrgicas estereolitografadas com apoio mucoso e que dispensam a necessidade de retalho cirúrgico, em casos selecionados. Esta técnica, denominada Cirurgia Guiada, tem sido descrita em inúmeras publicações em revistas especializadas e apresentada em diferentes congressos ao redor do mundo, tendo como principal característica a possibilidade de realização de procedimentos de maneira segura, rápida e com alto grau de previsibilidade. Este artigo tem por finalidade discutir as principais indicações clínicas, vantagens, e limitações da utilização de elementos diagnóstico e planejamento tridimensional em Implantodontia, além de descrever a seqüência do planejamento, cirurgia e prótese para tratamento do edentulismo mandibular com o sistema guiado Easy Guide - SIN.

The treatment planning of the edentulous lower jaw using software specially designed for use in Implantology has created the possibility of using the minimally invasive surgery procedures such as the flapless technique used in selected cases. This approach, named Guided Surgery has been described in several papers published in journals and presented in different meetings around the world, showing its main advantage, which is the possibility of treating the clinical cases in a simple and safe manner with high predictability and success rates. This paper has the aim to present the computed guided surgery, its clinical indications and limits, as well as the treatment planning, surgery and prosthetic details illustrated by a clinical case treated with the Easy Guide - S.I.N., surgical guide kit.

Prótese total fixa personalizada sobre implantes utilizando resina indireta: relato de caso clínico / Customized full arch fixed rehabilitation using indirect composite: case report

Atualmente os implantes são parte integrante do planejamento dos tratamentos odontológicos e a primeira opção nos tratamentos protéticos. Sua utilização tornou-se amplamente difundida devido à elevada taxa de sucesso comprovada cientificamente. Pacientes totalmente edêntulos passaram a usufruir dos benefícios biomecânicos e estéticos da prótese sobre implante, quando comparadas com as próteses convencionais. Com isso, o grau de conforto dos pacientes foi aumentado, bem como a satisfação do tratamento e a qualidade de vida. Dentre os materiais estéticos de revestimento utilizados na reabilitação com próteses totais fixas estão a resina acrílica, porcelana e resina composta indireta. Os dois primeiros são mais utilizados e apresentam diferentes propriedades mecânicas e físicas. A resina composta indireta apresenta propriedades mecânicas e físicas intermediárias entre os outros dois. Assim, este artigo tem o objetivo de apresentar o relato de caso clínico de reabilitação bi-maxilar com próteses totais fixas, utilizando a resina composta indireta Sinfony (3M ESPE), e discutir suas propriedades.

The osseointegrated implants are the first option in oral rehabilitation for many cases, as well as a fundamental tool for treatment planning. Its use has been improved dramatically during the last years due to the high success rates presented in several clinical trials in different parts of the world. The oral rehabilitation with osseointegrated fixed prosthesis presents mechanical and esthetic benefits if compared with conventional removable prosthesis, improving patients’ comfort and satisfaction, with a positive impact in their life quality. The acrylic resin and porcelain are the most used esthetic materials in oral rehabilitation supported by implants with different physical and mechanical properties. The indirect composite combines the positive properties of these two materials and might be seen as an option for this type of treatment. The aim of this study is to present a case report of a bi-maxillar full arch rehabilitation treated with fixed prosthesis having the indirect composite (Sinfony, 3M ESPE) as a customized esthetic material.

Aspectos contemporâneos das cerâmicas odontológicas / Contemporaneous aspects of dental carams

O potencial estético das cerâmicas odontológicas impulsionou a indústria de materiais , para o desenvolvimento de tecnologias que viessem a diminuir sua friabilidade, possibilitando a ampliação da indicação desses materiais para áreas posteriores, bem como para próteses parciais fixas. Existem no mercado odontológico, inúmeras opções de sistemas cerâmicos livres de metal, entretanto a grande diversidade de marcas comerciais podem gerar dúvidas durante a escolha do planejamento das próteses, sendo portanto, necessário um conhecimento a respeito das propriedades, vantagens, desvantagens e limitações de cada material, para que se possa indicá-los com segurança nas mais variadas situações clínicas. O objetivo do presente estudo foi rever a literatura a respeito dos sistemas cerâmicos disponíveis no mercado na atualidade, enfatizando suas propriedades, indicações e contra-indicações

Influência do método de processamento, sinterização convencional ou injeção a vácuo, na resistência à flexão e dureza de porcelanas feldspáticas / Effects of processing method on flexural strength, and hardness of feldspatic ceramics

O objetivo deste trabalho foi avaliar, por meio de ensaios de resistência à flexão, em três pontos, e de dureza, o comportamento mecânico das porcelanas feldspáticas Duceram Plus, Excelsior, Duceragold, Symbio, VMK, Omega 900 e Vitadur Alpha, submetidas a dois métodos de processamento laboratorial: sinterização convencional (fabricantes) e por injeção a vácuo (experimental). Foram confeccionadas dez amostras de cada grupo experimental para o ensaio de resistência à flexão (em forma de barra, 25mm de comprimento, 5mm de largura, 2mm de espessura - ISO 6872). Os testes foram realizados em equipamento MTS 810 (Material Test System, EUA), com célula de carga de 10kN e velocidade de 0,5mm/minuto, gerenciado por programa Test Star II (IBM, EUA). Para o ensaio de dureza, na escala Vickers, cinco fragmentos de cada grupo foram incluídos em resina acrílica autopolimerizável, polidos e submetidos ao teste em durômetro Buheler (EUA), com carga de 300gf, por 30 segundos. As cerâmicas Duceram Plus, Excelsior, Omega 900, Symbio e VMK 95 apresentaram maior resistência à flexão quando processadas por injeção. Os materiais Ducera Gold e Vitadur Alpha não sofreram qualquer influência deste método de processamento. O processo de injeção a vácuo, experimental, não alterou a dureza dos materiais estudados

The aim of this study was to compare the flexural strength and hardness of seven feldspatic ceramics (Duceram Plus, Excelsior, Duceragold, Symbio, VMK, Omega 900 and Vitadur Alpha) processed by convencional fusing and heat-pressing. Ten especimens were made for flexural test (25mm length; 5mm width; 2mm thick - ISO 6872). The tests were realized in a MTS 810 machine (Material Test System - USA), with a 10kN load cell and crosshead-speed of 0.5mm/minute, managed by Test Star II software (IBM, USA). Five samples of each ceramic were included in autocured resin JET (Artigos odontológicos Clássico, Brazil), polished and submitted to Vickers hardness test in duromer Buheler (USA), with load of 300gf, for 30 seconds. Results showed that the ceramics Duceram Plus, Excelsior, Omega 900, Symbio and VMK 95 presented higher flexural stengths values when heat-pressed. Ducera Gold and Vitadur Alpha flexural stengths values weren´t affected by the processing method. Processing method (convencional fusing and heat-pressed) did not influenced the hardness of materials evaluated

Influência do método de processamento, sinterização convencional ou injeção a vácuo, na resistência à flexão e dureza de porcelanas feldspáticas / Effects of processing method on flexural strength, and hardness of feldspatic ceramics

O objetivo deste trabalho foi avaliar, por meio de ensaios de resistência à flexão, em três pontos, e de dureza, o comportamento mecânico das porcelanas feldspáticas Duceram Plus, Excelsior, Duceragold, Symbio, VMK, Omega 900 e Vitadur Alpha, submetidas a dois métodos de processamento laboratorial: sinterização convencional (fabricantes) e por injeção a vácuo (experimental). Foram confeccionadas dez amostras de cada grupo experimental para o ensaio de resistência à flexão (em forma de barra, 25mm de comprimento, 5mm de largura, 2mm de espessura - ISO 6872). Os testes foram realizados em equipamento MTS 810 (Material Test System, EUA), com célula de carga de 10kN e velocidade de 0,5mm/minuto, gerenciado por programa Test Star II (IBM, EUA). Para o ensaio de dureza, na escala Vickers, cinco fragmentos de cada grupo foram incluídos em resina acrílica autopolimerizável, polidos e submetidos ao teste em durômetro Buheler (EUA), com carga de 300gf, por 30 segundos. As cerâmicas Duceram Plus, Excelsior, Omega 900, Symbio e VMK 95 apresentaram maior resistência à flexão quando processadas por injeção. Os materiais Ducera Gold e Vitadur Alpha não sofreram qualquer influência deste método de processamento. O processo de injeção a vácuo, experimental, não alterou a dureza dos materiais estudados.